The present invention relates to a retractable cargo bed of a truck, van or other service body vehicle.
U.S. Pat. No. 5,513,941 (Kulas et al 1996) is an example of a retractable cargo bed. Such retractable cargo beds consist of a stationary frame which is adapted for mounting to a deck of a truck, van or other service vehicle, and a travelling frame which slides along the stationary frame. It is important that the retractable cargo beds have reliable locking mechanisms which prevent the uncontrolled movement of the travelling frame relative to the stationary frame. In the absence of a reliable locking mechanism, the travelling frame could extend uncontrollably. This is particularly the case when the truck is parked on a hill and the travelling frame is heavily loaded. Should the travelling frame extend uncontrollably, a person could be struck and sustain injuries. In severe cases, the person could become crushed against a wall or parked vehicle.
The Kulas et al reference has a locking mechanism which consists of a pin structure referred to as a xe2x80x9cnipplexe2x80x9d which is carried by a spring biased lever mounted on the travelling frame. The lever biases the pin into engagement with any one of a plurality of apertures positioned at spaced intervals along the stationary frame. Although the locking mechanism illustrated in the Kulas et al reference is better than many on the market, there is a fundamental flaw in a pin and aperture type of system. Under conditions when the locking mechanism is needed the most, the momentum of the travelling frame does not provide an opportunity for the pin to engage the apertures. As a result the pin travels rapidly past each aperture and the locking mechanism does not engage.
What is required is a retractable cargo bed with a more reliable locking mechanism.
According to the present invention there is provided a retractable cargo bed which includes a stationary frame adapted for mounting onto a deck of a truck, van or other service body vehicle. The stationary frame has a first end, a second end, a bottom and opposed sides having guide channels. A travelling frame is provided having a first end, a second end and opposed sides. The travelling frame is received within the stationary frame with the opposed sides of the travelling frame engaging the guide channels on the opposed sides of the stationary frame. The travelling frame is movable relative to the stationary frame between a retracted position and an extended position. A locking mechanism for controlling travel of the travelling frame along the stationary frame is provided which includes stop members secured to the bottom of the stationary frame at spaced intervals from the first end to the second end of the stationary frame. A locking lever is carried by the travelling frame. The locking lever is pivotally mounted for movement about an axis which is parallel to the longitudinal axis of the travelling frame between a downwardly angled locking position and a substantially horizontal release position. Means is provided for biasing the locking lever into the locking position whereby the locking lever engages one of the stop members secured to the bottom of the stationary frame. A release lever is provided for manually moving the locking lever to the release position.
The retractable cargo bed, as described above, with a locking lever that engages a stop member anchored to the bottom of the stationary frame, consistently engages even when the travelling frame is moving rapidly under heavy load.
Although beneficial results may be obtained through the use of the retractable cargo bed, as described above, it is preferred that the locking mechanism include an activation rod which extends from the first end to the second end of the travelling frame. The activation rod has a first end positioned adjacent to the first end of the travelling frame and a second end positioned adjacent to the second end of the travelling frame. The activation rod has a longitudinal axis and is mounted to the travelling frame for rotation about the longitudinal axis. The release lever is secured to the first end of the activation rod. The locking lever is secured to the second end of the activation rod.
Although beneficial results may be obtained through the use of the retractable cargo bed, as described above, the more rigid the activation rod can be maintained, the better the locking mechanism will work. Even more beneficial results may, therefore, be obtained when a plurality of transverse structural members extend between the opposed sides of the travelling frame and the activation rod extends through and is rigidly supported by the transverse structural members.
Although beneficial results may be obtained through the use of the retractable cargo bed, as described above, the preferred means of biasing the locking lever into the locking position is through the use of a spring. It is preferred that the spring exert a rotational force upon the activation rod to urge the locking lever into the locking position.
Although beneficial results may be obtained through the use of the retractable cargo bed, as described above, beneficial results have been obtained when the stop members are metal plates horizontally mounted in an angular orientation to guide the locking lever in against the stationary frame.
Although beneficial results may be obtained through the use of the retractable cargo bed, as described above, instead of the locking mechanism acting upon one of the sides, it is preferred that the stop members be secured to a centrally positioned longitudinal structural member on the stationary frame.
Although beneficial results may be obtained through the use of the retractable cargo bed, as described above, another problem often experienced with retractable cargo beds is a twisting of the stationary frame which occurs when the travelling frame is fully extended under load. Even more beneficial results may, therefore, be obtained when rigidifying reinforcing members extend down the opposed sides of the stationary frame.
Although beneficial results may be obtained through the use of the retractable cargo bed, as described above, another problem often experienced with retractable cargo beds is a pitching forward and downward of the travelling frame when fully extended. Even more beneficial results may, therefore, be obtained when the guide channels of the stationary frame have a top plate and a bottom plate, and the travelling frame has a top roller at the second end that engages the top plate and a bottom roller at the second end that engages the bottom plate. With this construction the second end of the travelling frame is supported both top and bottom when in a fully extended position.